Transport Scotland Scottish Trunk Road Infrastructure Project Evaluation - 1YA Evaluation Report for A77(T) Park End to Bennane
3 A77(T) Park End to Bennane
3.1 Introduction
Project Description
The A77(T) between Girvan and Stranraer is approximately 46km in length, and is located across the South Ayrshire and Dumfries and Galloway Council areas. It is an important strategic road in the south-west of Scotland, linking Glasgow and the Central Belt with Ayrshire and the Loch Ryan ferry ports.
The A77(T) Park End to Benanne project involved the improvement and widening of the existing A77(T) over approximately 2.9 kilometres to provide unambiguous, guaranteed overtaking in both directions through the provision of wide single 2+1 carriageway (WS2+1). The layout of the WS2+1 scheme is such that approximately 0.7 kilometres of unambiguous overtaking is provided in each direction, with the 2-lane overtaking sections facing each other on approach to the changeover.
The general location of the project is shown in Figure 3.1.
The A77(T) Park End to Bennane project was officially opened to traffic in July 2011.
Rationale and mandate for the scheme
The project was implemented in conjunction with the wider Route Action Plan for the A77(T), which included a number of other overtaking projects on the A77(T) which are reported within previous evaluation reports.
In combination with other overtaking projects on the A77(T), the Park End to Bennane scheme was targeted principally to break up platoons created by either slower moving agricultural vehicles or traffic disembarking from Irish Sea ferries.
The decision to invest in the scheme was made by Transport Scotland in July 2008.
Project Objectives
The objectives of the A77(T) Park End to Bennane project were set as follows:
- To improve and increase the number of overtaking opportunities to eradicate conflicts between long distance users and local / agricultural traffic;
- To improve the operational performance and level of services and safety on the A77(T) by reducing the effects of driver stress and journey times; by constructing dedicated overtaking sections designed to break up the effects of convoys / platoons of vehicles;
- To maintain the asset value of the A77(T) route;
- To mitigate the environmental impact of the new works where possible; and
- To achieve good value for money for both tax payers and transport users.
3.2 Evaluation Methodology
As set out in Section 2.1, this report presents the results of a 1YA Opening Evaluation of the A77(T) Park End to Bennane project, focusing on:
- The operation of the scheme: how the scheme is operating (in terms of traffic and safety in particular); and
- Objectives: whether the scheme is on-track to achieve its objectives.
A process evaluation has been carried out, which considers how the project was implemented across the elements of programme and key processes. As commentary on this is included under other criteria (e.g. RSA process under Safety), the main aspects of process evaluation have been summarised above in the Executive Summary (Section 1 of this report) for ease of reference.
This evaluation was supported by a site visit carried out on 2nd August 2013. External stakeholder views were invited from South Ayrshire Council and Stena Line. These are presented throughout the report.
3.3 The operation of the scheme and process evaluation
Network Traffic
The evaluation is supported by the consideration of pre and post opening comparison of operational indicators, which focuses on network traffic indicators including traffic volumes and travel times, presented in the following section.
Traffic Volumes
The locations of the Automatic Traffic Counters (ATC) within the study area are shown in Figure 3.1.
Comparison Between Pre and Post Opening Traffic Flows
The Annual Average Daily Traffic (AADT) flows pre and post project opening on the A77(T) route within the vicinity of the project are presented in Table 3.1.
A comparison between pre and post opening traffic volumes on the A77(T) within the vicinity of the scheme indicates that traffic flows in 2012 were broadly consistent with 2007 and 2009 flow levels. Traffic volumes between 2010 and 2012 reduced by approximately 100 vehicles per day (vpd) (3%).
Given the nature of the A77(T) Park End to Bennane project, changes in traffic are not likely to be as a consequence of changes to the carriageway standard and may be as a result of reductions in traffic volumes across the wider trunk road network due to the economic downturn experienced during the evaluation period.
Comparison Between Predicted and Actual Traffic Flows
The opening year flow comparisons for the A77(T) Park End to Bennane project are based on AADT flows from 2012 as this was the first full year of reliable traffic data available from Transport Scotland's traffic counters within the vicinity of the project.
As part of the project's appraisal, National Road Traffic Forecasts (NRTF) low and high traffic growth factors were applied to the 2004 base year traffic flows to derive opening and future modelled assessment year traffic flows.
Predicted traffic flows for 2012 have been derived by interpolating between the modelled assessment year design network flows.
A summary of the actual and predicted traffic data is shown in Table 3.2 below.
* 2012 flows (first full year of ATC data available)The comparison between predicted and actual AADT flows in Table 3.2 indicates that the predicted 2012 flow (derived by interpolating between the modelled assessment year traffic flows) was 1.6% lower and 3.3% greater than the observed 2012 flow under low and high traffic forecast scenarios respectively, which is well within accepted limits.
Overtaking Opportunities
Comparison Between Pre and Post Opening Overtaking Opportunities
A post opening overtaking survey was undertaken on the A77(T) in November 2011 to provide an indication of conditions within the vicinity of the Park End to Bennane project.
The pre and post opening surveys recorded the number of overtaking manoeuvres, platooning and vehicle speeds on the A77(T) in both directions of travel within the direct vicinity of the project and on the single carriageway sections on approach to the project's location.
The results from the post opening survey were compared against the results from a pre-opening survey undertaken in March 2004 to provide an indication of the effect that the project has had on overtaking conditions.
The level of overtaking pre and post opening is shown in Table 3.3 below.
|
|
AM Survey Period |
PM Survey Period |
||
|---|---|---|---|---|
|
Northbound |
Southbound |
Northbound |
Southbound |
|
|
Pre Opening |
19% |
5% |
22% |
12% |
|
Post Opening |
17% |
14% |
19% |
17% |
A comparison between the percentage of vehicles that carried out an overtaking manoeuvre during the pre and post opening surveys suggests that the A77(T) Park End to Bennane scheme has increased overtaking in the southbound direction but reduced overtaking in the northbound direction over the extents of the survey site.
The percentage of northbound vehicles that carried out an overtaking manoeuvre during the pre-opening survey AM and PM periods was 19% and 22% respectively, which can be compared to 17% and 19% respectively during the post opening survey.
In the southbound direction, 5% and 12% of all southbound vehicles that travelled through the survey site during the pre-opening survey AM and PM survey periods respectively carried out an overtaking manoeuvre, which can be compared against 14% and 17% respectively during the post opening survey.
It is noted, however, that temporary roadworks were present on site to the north of Ballantrae on the day of the pre opening survey which comprised a section of temporary shuttleworking controlled by traffic signals.
A review of the pre opening survey data suggests that, as a result of the works, southbound drivers (who would have had advanced warning of the roadworks) may not have performed overtaking manoeuvres on approach to the shuttleworking section. Conversely, northbound drivers (who would have been in platoons as a result of the temporary traffic signals) may have been inclined to overtake slower moving vehicles when pulling away from the roadworks.
Due to the temporary roadworks present on the day of survey within the vicinity of the survey site, it is considered that the results of the pre opening survey for the Park End to Bennane scheme are not representative of typical operating conditions and, as such, it is difficult to draw any firm conclusions from the comparison of the level of overtaking manoeuvres carried out during the pre and post opening surveys.
Comparison Between Pre and Post Opening Platoons
Pre and post opening platooning data, collected as part of the pre and post opening overtaking surveys, was available for the AM and PM survey periods.
The results from the post opening survey were compared against the results from a pre-opening survey undertaken in March 2004 to provide an indication of the effect that the project has had on platooning conditions.
The level of platooning pre and post opening is shown in Tables 3.4a and 3.4b below. "Enter" indicates the point at which vehicles enter the 2.9km section whereas "Exit" indicates the point at which vehicles leave the section.
The post opening survey indicated that the total number of platoons that exited the survey site in the northbound direction during the AM survey period and in the southbound direction during the PM survey period were less than the total number that entered the site. The post opening survey also indicated that the total number of platoons that exited the survey site in the southbound direction during the AM survey period and in the northbound direction during the PM survey period were greater than the total number that entered the site.
Examination of the results suggests that the number of platoons of three vehicles or more generated through the dispersion of vehicles in 'larger' platoons were not outweighed by the number of vehicles that were no longer in platoon as they exited the site due to the dispersion of 'smaller' platoons.
A comparison between the total number of platoons that entered and exited the survey site during the pre and post opening surveys suggests that, overall, the A77(T) Park End to Bennane scheme has a positive effect on the dispersion of vehicles in platoon as a consequence of the increase in vehicles carrying out overtaking manoeuvres.
It is noted, however, that due to temporary roadworks in the vicinity on the day of the pre opening survey, the proportion of vehicles recorded as traveling in a longer platoon was much greater than typically observed at this site, particularly in the northbound direction of travel. As such it is considered that the results of the pre opening survey for the Park End to Bennane scheme are not representative of typical operating conditions and, therefore, it is difficult to draw any firm conclusions from the comparison of the number of platoons occurring during the pre and post opening surveys.
Stakeholder feedback
Stena Line Ltd, who operate ferry services at Cairnryan, was invited to offer feedback on the A77(T) Park End to Bennane scheme. Their overall perception of the scheme was that it had a neutral impact on traffic using their services. South Ayrshire Council were also asked for their views on the scheme - their feedback suggested it had positively facilitated opportunities for overtaking and led to improved travel times. South Ayrshire Council noted that when linked to previous improvements on the route, the scheme had facilitated opportunities for overtaking between Ballantrae and Lendalfoot, a stretch of nearly 6 miles.
Travel Times
Comparison Between Pre and Post Opening Journey Times
Mean vehicle speeds during the AM and PM survey periods, estimated from the information collected as part of the pre and post opening overtaking surveys, have been used as a proxy for changes in travel times.
A comparison between the mean vehicle speeds observed during the pre and post opening overtaking surveys is shown in Table 3.5.
The comparison between mean vehicle speeds over the extents of the survey site indicate that speeds in both directions of travel have increased within the vicinity of the Park End to Bennane project, however, the pre opening survey is not considered representative of typical operating conditions as a result of temporary roadworks present on the day of survey which impacted on vehicle speeds in both the northbound and southbound directions of travel. As such, it is difficult to draw any firm conclusions from the comparison of the mean vehicle speeds observed during the pre and post opening surveys.Based on the distances between the cameras used for the post opening survey, mean southbound vehicle speeds have been estimated to exceed the national speed limit in force over the extent of the survey site.
3.4 Environment
The following section provides a summary of the assessment of environmental mitigation measures proposed for the A77(T) Park End to Bennane scheme. A fuller report is provided in Appendix B.
Review of Environmental Mitigation Measures
The environmental mitigation measures originally proposed for the A77(T) Park End to Bennane project were obtained from the project's ES[1]. A review of the environmental mitigation measures was carried out in August 2013, as well as a review of the as-built scheme plans. Following this review a site visit was undertaken to establish whether or not the proposed mitigation measures as set out in the Schedule of Committed Mitigation within the ES had been implemented.
The ES for the scheme proposed mitigation measures to address impacts under the following criteria:
- Water Quality, Drainage and Flood Defence
- Biodiversity and Habitats
- Landscape
- Visual Amenity
- Cultural Heritage
- Physical Fitness
Findings
The proposed scheme was not considered to generate any additional traffic, and therefore no issues were identified in relation to noise and vibration, global and local air quality.
Much of the mitigation which was included within the ES has been implemented on site and is in good condition. The site inspection did identify some potential issues relating to the construction of footways at certain locations which did not appear to tie into a contiguous path network or result in any immediately obvious benefit to the environment and pedestrians of the surrounding area. Each path is located at a crossing of the A77 where footways to the west of the scheme provide access to the shore. Consultation with affected proprietors during the scheme's design indicated that the footways accessing the shore were in occasional use and provided access to properties associated with Ballig Farm.
The A77(T) Park End to Bennane scheme fits well within the existing landscape and the wider, mixed grass verges and the retention (and addition) of stone walls along the length of the route further integrate the scheme into the existing environment.
The scheme integrates well with the climbing lane scheme to the north, as well as creating an effective entrance into the village of Ballantrae to the south, which has been integrated so as to encourage motorists to reduce their speed when approaching the village.
Environment: Key Findings
Much of the mitigation which was included within the ES has been implemented on site and is in good condition.
The site inspection identified some potential issues related to the implementation of footways at certain locations which do not tie into a path network or seem to result in any obvious benefit to the environment and pedestrians of the surrounding area. Consultation with affected proprietors during the scheme's design confirmed the need for the provision of footways at these locations.
Key recommendations
It is recommended that the review of environmental mitigation measures proposed for future schemes continues to be undertaken during the detailed design process to determine whether the recommended mitigation is appropriate to the overall scheme.
3.5 Safety
Accidents
Comparison Between Pre and Post Opening Personal Injury Accident Numbers
The locations and severities of accidents occurring within the vicinity of the A77(T) Park End to Bennane project 3 years before and 1 year after project completion are shown in Figures 3.2a and 3.2b.
A summary of the personal injury accident data is shown in Table 3.6.
|
Period |
Fatal |
Serious |
Slight |
Total Accidents |
|---|---|---|---|---|
|
3 Years Before |
||||
|
A77(T) |
0 |
0 |
1 |
1 |
|
1 Year After |
||||
|
A77(T) |
0 |
0 |
0 |
0 |
As can be seen from Table 3.6, no personal injury accidents occurred in the 1 year period following the opening of the project in comparison to one personal injury accident (slight) in the 3 years before opening, suggesting a potential improvement in road safety.
Road Safety Audits
The RSA process has been followed, with Stage 1, 2, 3 and 4 Audits carried out. The Stage 4 RSA report examined the 3 year period prior to construction (30 September 2007 to 1 October 2010) and the 1 year period following opening. The Stage 4 RSA confirmed that no accidents had occurred within the vicinity of the scheme following opening and confirmed that no trends or common factors in accidents had been observed.
Safety: Key Findings
An assessment of the 1 year post opening personal injury accidents and the findings from the Stage 4 RSA suggests that the A77(T) Park End to Bennane project is operating safely.
Recommendations
The Stage 4 RSA suggests that the scheme should continue to be monitored to confirm that it is operating satisfactorily.
Transport Economic Efficiency
Recommended changes to the design standards, set out in DMRB Volume 6, TD 70/08 - Design of Wide Single 2+1 Roads, were introduced during the project's construction. As a result of implementing these changes, the length of the overtaking section provided is shorter than that modelled during the project's appraisal. It is therefore likely that the level of overtaking has been over predicted and consequently the economic benefits of the project will be less than predicted.
Comparison Between Predicted and Actual Traffic Flows
The comparison indicates that the predicted 2012 flows were within 3.3% of the observed 2012 flows on the A77(T) within the vicinity of the Park End to Bennane scheme, which is well within accepted limits.
Stakeholder feedback
Stena Line Ltd commented that this specific scheme, on its own, had not any observable impact on their ferry operations.
Economy: Key Findings
The difference between predicted and actual AADT flows suggests that the economic benefits are in line with that predicted. As the length of overtaking provided is shorter than that modelled, the economic benefits of the project may be less than predicted.
Investment Costs
Comparison Between Predicted and Out-turn Costs
The out-turn and predicted project costs are shown in Table 3.7.
Cost to Government: Key Findings
The out-turn cost of the A77(T) Park End to Bennane project is approximately £0.11m (3%) greater than was predicted at the time of assessment.
3.8 Value for Money
Initial Indications
The economic appraisal results for the A77(T) Park End to Bennane project predicted a Net Present Value (NPV) of £0.74m and Benefit to Cost Ratio (BCR) of 1.26 under the 60/40 traffic forecast scenario.
Based on the comparisons presented in Sections 3.6 and 3.7, which suggest that the benefits may have been overestimated and indicate that the out-turn cost is greater than predicted, the NPV and BCR of the project are unlikely to be as great as predicted.
Value for Money: Key Findings
Although the NPV and BCR are unlikely to be as great as predicted at the time of assessment as a consequence of reduced traffic levels as a result of the economic downturn, it is judged that the project will continue to provide benefits to road users.
3.9 Progress Towards Achieving Objectives
As specific indicators to measure the performance of the A77(T) Park End to Bennane project against its objectives have not been developed, an initial indication of how the project is progressing towards achieving its objectives is based on the pre opening data available, supplemented by post opening data collected as part of the evaluation.
Initial Indications
A summary of the evaluation, providing an indication of how the A77(T) Park End to Bennane project is progressing towards achieving its objectives, is presented in Table 3.8.
|
Key: |
+ve |
Initial indication(s) that objective may be achieved |
|
|
= |
Progress towards achievement of objective cannot be confirmed |
|
|
O |
Initial indication(s) that objective may not be achieved |